<p>PDL (performance description language) is a high-level performance modeling language that offers a way to generate valuable design analysis data. Designers can write generic performance models in PDL and, for specific designs, compile them into executable versions. The PDL system can then process performance data and generate detailed graphs that can be used for analysis. PDL theory is embedded into designer-friendly language constructs to permit succinct and readable performance models. And because the PDL evaluator supports incremental attribute evaluation, the performance models can be partially evaluated. PDL is a step toward further development of robust general-purpose environments for performance modeling and evaluation. </p>